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  <div class="section" id="using-wildcard-imports-from-import">
<h1>using wildcard imports (<cite>from … import *</cite>)<a class="headerlink" href="#using-wildcard-imports-from-import" title="Permalink to this headline">¶</a></h1>
<p>When an import statement in the pattern of <code class="docutils literal notranslate"><span class="pre">from</span> <span class="pre">MODULE</span> <span class="pre">import</span> <span class="pre">*</span></code> is used it may become difficult for a Python validator to detect undefined names in the program that imported the module. Furthermore, as a general best practice, import statements should be as specific as possible and should only import what they need.</p>
<div class="section" id="anti-pattern">
<h2>Anti-pattern<a class="headerlink" href="#anti-pattern" title="Permalink to this headline">¶</a></h2>
<p>The following code imports everything from the <code class="docutils literal notranslate"><span class="pre">math</span></code> built-in Python module.</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="c1"># wildcard import = bad</span>
<span class="kn">from</span> <span class="nn">math</span> <span class="kn">import</span> <span class="o">*</span>
</pre></div>
</div>
</div>
<div class="section" id="best-practices">
<h2>Best practices<a class="headerlink" href="#best-practices" title="Permalink to this headline">¶</a></h2>
<div class="section" id="make-the-import-statement-more-specific">
<h3>Make the <code class="docutils literal notranslate"><span class="pre">import</span></code> statement more specific<a class="headerlink" href="#make-the-import-statement-more-specific" title="Permalink to this headline">¶</a></h3>
<p>The <code class="docutils literal notranslate"><span class="pre">import</span></code> statement should be refactored to be more specific about what functions or variables it is using from the <code class="docutils literal notranslate"><span class="pre">math</span></code> module. The modified code below specifies exactly which module member it is using, which happens to be <code class="docutils literal notranslate"><span class="pre">ceil</span></code> in this example.</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">math</span> <span class="kn">import</span> <span class="n">ceil</span>
</pre></div>
</div>
</div>
<div class="section" id="import-the-whole-module">
<h3>Import the whole module<a class="headerlink" href="#import-the-whole-module" title="Permalink to this headline">¶</a></h3>
<p>There are some cases where making the <code class="docutils literal notranslate"><span class="pre">import</span></code> statement specific is not a good solution:</p>
<ul class="simple">
<li><p>It may be unpractical or cumbersome to create or maintain the list of objects to be imported from a module</p></li>
<li><p>A direct import would bind to the same name as that of another object (e.g. from asyncio import TimeoutError)</p></li>
<li><p>The module that the object is imported from would provide valuable contextual information if it is right next to the object when it’s used.</p></li>
</ul>
<p>In these cases, use one of these idioms:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">math</span>
<span class="n">x</span> <span class="o">=</span> <span class="n">math</span><span class="o">.</span><span class="n">ceil</span><span class="p">(</span><span class="n">y</span><span class="p">)</span>

<span class="c1"># or</span>

<span class="kn">import</span> <span class="nn">multiprocessing</span> <span class="k">as</span> <span class="nn">mp</span>
<span class="n">pool</span> <span class="o">=</span> <span class="n">mp</span><span class="o">.</span><span class="n">Pool</span><span class="p">(</span><span class="mi">8</span><span class="p">)</span>
</pre></div>
</div>
</div>
</div>
<div class="section" id="references">
<h2>References<a class="headerlink" href="#references" title="Permalink to this headline">¶</a></h2>
<ul class="simple">
<li><p><a class="reference external" href="http://stackoverflow.com/questions/15145159/importing-modules-how-much-is-too-much">Stack Overflow - Importing Modules</a></p></li>
<li><p><a class="reference external" href="http://stackoverflow.com/questions/710551/import-module-or-from-module-import">Stack Overflow - ‘import module’ or ‘from module import’</a></p></li>
</ul>
</div>
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